I'm building a full-size J-3 replica, and the numbers sure point to a VW conversion. However, I spoke with Great Plains, and the only way it would work well on a plane like this (lots of drag) is with a reduction drive. So there go any weight savings over a Continental A65, and the complexity of the redrive is an added headache. The reason a redrive is needed is to get enough torque for the prop to convert to thrust. I've run the numbers on a few engines, and nothing in the 65 HP family produces as much torque as a Cont. A65. The prices are good, it's simple and proven, and the weight is reasonable. My plane was designed around the Rotax 582, but I'm scared of 2-strokes. I looked hard at the Hirth engines, but they're expensive, and they're still 2-strokes (and still don't put out the torque of an A65).